To manufacture a semiconductor integrated circuit, various processing is generally applied to a semiconductor wafer comprising a silicon substrate or the like, such as film deposition, etching, oxidation, diffusion, modification, etc. Among the above sorts of processing, for example, representative oxidation processing includes oxidation of the surface of a polysilicon film or a single crystal film and oxidation of a metal film. Particularly, the oxidation processing is used in forming mainly a gate oxide film and an insulating film for a capacitor or a floating gate of a nonvolatile memory cell and the like
The methods for the oxidation processing are categorized in terms of pressure as an atmospheric oxidation method performed inside a processing container with an atmosphere equivalent of a substantial atmospheric pressure and a vacuum oxidation method performed in a processing container with a vacuum atmosphere. In terms of classification of the gas used for oxidation, there are for example a wet oxidation method (e.g. the official gazette of Japanese Patent Application Publication No. Hei 3-140453/1991) in which hydrogen and oxygen are combusted by external combustion equipment to produce water vapor which is used to perform oxidation, and a dry oxidation method (e.g. official gazette of Japanese Patent Application Publication No. Sho 57-1232/1982) in which oxidation is performed without using water vapor whereas only ozone or oxygen is supplied into a processing container for example.
For the meantime, recent attention is drawn to an insulating film structure in which an oxide film, e.g. SiO2 film, is laminated on the upper layer of a nitride film, as typified by SiN (a silicon nitride film) for example, due to the characteristics of outstanding heat resistance, insulating ability, etc.
Generally, an insulating film structure of this sort is developed by depositing SiO2, by thermal CVD (Chemical Vapor Deposition), on a SiN film formed on the surface of a silicon substrate or the like